Ralf Schumacher has denied telling a German newspaper that he expected his older brother Michael would retire soon from Formula One.

"We barely mentioned Michael, that's the strange thing about it," the Toyota driver told reporters at the US Grand Prix on Thursday when asked about the reported comments in Sport Bild this week.

"We were talking about Ferrari, that they have a difficult year and he asked me why they have a difficult time, was it only [tyre partner] Bridgestone? I said I doubted that it was only Bridgestone's fault," he said.

"And that was about it. I have never mentioned that Michael is going to stop or whatever so it's really weird.

"I have no clue. I haven't asked," he added when asked what he did think of his brother's intentions.

"Michael is the only guy to ask about that. I have no idea about it and to be honest I don't care. It's great to have him here and I have no reason on Earth for him to stop and I wouldn't think about it."

Ferrari's Schumacher, the seven-times world champion who has yet to win this year and is now the oldest driver in the sport at 36 years old, dismissed suggestions he was not enjoying racing any more.

"I don't know how he comes up with that," he said of Ralf's reported comments. "I mean, as much as I speak with you, I speak with him and tell him how much I enjoy it actually.

"Even though I'm not winning, you can enjoy it. You don't always need to win to be happy...I'm not lacking fun and neither do I lack motivation."